Electronic speed responsive device



Aug. 21, 1962 D. E. CLARK ELECTRONIC SPEED RESPONSIVE DEVICE 2 Sheets-Sheet 1 Filed Aug. 19, 1958 TO AFTERBURNER T, UNIT 45 N0 2 RECTIFIER o a RELAY INVENTOR. DONALD E. CLARK M W ATTO EYS ,1962 D. E. CLARK 3,049,879

ELECTRONIC SPEED RESPONSIVE DEVICE Filed Aug. 19, 1958 2 Sheets-Sheet 2 14 TO 8O CYC. FILTER l9 "W TO 290 CYC, FILTER Fig- 5' INVENTOR.

. DONALD E. OLARK cam M LM ATTOR EYS United States Patent Qfiice 3,049,879 Patented Aug. 21, 1962 3,049,879 ELECTRONIC SPEED RESPONSIVE DEVICE Donald E. Clark, Ninevah, N. assignor to The Bendix Corporation, a corporation of Delaware Filed Aug. 19, 1958, Ser. No. 756,023 3 Claims. (Cl. 60-39.14)

This invention relates to an electronic speed responsive device.

In the embodiment of the speed responsive device shown herein the device is responsive to a plurality of difierent rotation-a1 speeds, and is particularly adapted for the control of appurtenant mechanisms associated with the rotating shaft which controls the speed responsive device. An illustrative rotational speed responsive device is a switch used with a jet engine for controlling the ignition and afterburner systems thereof. A typical jet engine equipped with an afterburner requires the ignition system to be energized at speeds of roughly to 825 rpm, of a subordinate shaft rotating in synchronism with the engine, and for the ignition system to be deenergized at all speeds of such subordinate shaft from roughly 825 to 3600 r.p.m. and above, the flame in the engine being then self-sustaining. Such engine also requires the afterburner system to be deenergized in a subordinate shaft speed range from 0 to generally 2905 r.p.m., and to be energized for all speeds higher than 2905 rpm.

Such functions of controlling the ignition and afterburner systems have in the past been performed by switches of the centrifugal type. Such switches, however, are far from accurate, since the speeds at which they operate are significantly alfected by varying friction between the parts, such as caused by Wear or dimensional variations due to temperature changes. The speed responsive device of the present invention is substantially wholly electronic in nature and is thus free from variations in its manner of operation caused by differences in friction, temperature, etc.

The invention has among its objects the provision of a novel electronic speed responsive device.

A further object of the invention resides in the provision of an electronic speed responsive device which consists largely of simple filter circuits whereby the device is initially accurate and remains so throughout the long operating life.

Yet another object of the invention resides in the provision of an electronic speed responsive device which is economical to make and maintain, and the operation of which remains substantially constant in character despite wide variations of operating temperature to which it is subjected.

The above and further objects and novel features of the invention will more fully appear from the following description when the same is read in connection with the accompanying drawings. It is to be expressly understood, however, that the drawings are for the purpose of illustration only and are not intended as a definition of the limits of the invention.

In the drawings, wherein like reference characters refer to like parts throughout the several views,

FIG. 1 is a somewhat schematic block diagram of the circuit of an illustrative embodiment of electronic speed responsive device made in accordance with the invention;

FIG. 2 is a schematic wiring diagram of a first rectifier and relay employed in the device of FIG. 1;

FIG. 3 is a schematic wiring diagram of a second rectifier and relay employed in the device of FIG. 1;

FIG. 4 is a wiring diagram of a low frequency filter component of the device of FIG. 1;

FIG. 5 is a wiring diagram of a high frequency filter component of the device of FIG. 1; and

FIG. 6 is a wiring diagram of an L pad attenuator employed in the device of FIG. 1 in advance of the filters thereof.

Turning now to the drawings, in FIG. 1 there is shown the wiring diagram of an electronic speed responsive d vice which is used in the above discussed application of controlling the ignition and afterburner systems of a jet engine. Such device includes an alternator schematically shown at 10, such alternator being driven by a shaft 13 which in this instance is a subordinate shaft connected to rotate in synchronism with the main shaft of the engine. It will be understood that in some instances the alternator may be directly connected to the main shaft of an engine or other device being controlled. Alternator 10 is of such design as to feed an alternating current through output wire 11, the frequency of such generated current hearing a fixed relationship to the speed of rotation of shaft 13.

In the described illustrative embodiment, alternator 10 has a twelve pole stator with a rotor in the form of a four pole permanent magnet rotating therewithin. With such construction the ratio between the revolutions per minute of shaft 13 and the cycles per second of the alternating current delivered to wire 11 is 10:1. The alternator output is delivered to an L pad attenuator 12 to e specifically described in connection with FIG. 6, and thence through one branch wire 14 to an 80 cycle (per second) high pass filter 15 from which the output is led through a wire 16 to a first rectifier and relay unit 17 which controls the ignition system of the engine. Another branch wire 19 from attenuator 12 leads to a 290 cycle pass filter 2%). The output from filter 20 is led through wire 21 to a second rectifier and relay unit 22 which controls the afterburner system of the engine. Each of the units 12, 15, 17, 20, and 22 is grounded, as is one output lead from generator 10.

Unit 17 is made up of a rectifier unit 24 and a relay unit 27, as shown in FIG. 2. Rectifier unit 24 consists of a closed loop of four serially connected half-wave rectifiers 5 -8 one corner of the thus formed bridge being connected to wire 16; the opposite corner of the loop or bridge is connected to ground. A further, different corner of the bridge is connected to one end of coil 29 of relay 27 by wire 25, the fourth corner of the bridge being connected by a wire 26 to the other end of coil 29 of the relay. The relay 27 has a movable contactor 30 connected to a central terminal 31. Contactor 30 is movable between an upper fixed contact connected to a terminal 32 and a lower fixed contact connected to a terminal 34. The relay 27 is of such construction that contactor 36 is constantly urged toward the upper position shown in FIG. 2 in which circuit 31, 30, 32, is closed and thereby to energize the ignition system of the engine. When, however, a sufiicient voltage diiference exists between wires and 26, coil 29 of the relay 27 is energized sufficiently to move contactor downwardly, thereby opening the circuit 31, 30, 32, and deenergizing the ignition system.

The second rectifier and relay unit 22 shown in detail in FIG. 3 is substantially similar to unit 17. Rectifier unit 35 of unit 22 has a closed loop consisting of four serially connected half-wave rectifiers 8 -8 which are connected to their supply wire (21) and to ground in the same manner as in unit 24. Delivery wires 36 and 37, connected to opposite corners of the loop or bridge, are connected to opposite ends of coil 40 of relay 39. Relay 39, which is generally similar to relay 27, has a movable contactor 41 which is biased toward its upper position in which circuit 42, 41, 45 is open. When relay 39 is energized by the existence of a sufiicient dilference in potential between the wires 36 and 37, contactor 41 is moved downwardly to complete circuit 42, 41, 45, thereby to initiate operation of the afterburner.

The first, cycle high pass filter 15 is shown in detail in FIG. 4. Input wire 14 has two serially connected condensers C and C interposed between it and delivery wire 16; an opposed conductor 18 is connected to ground. Between wire 14 and conductor 18 at a position in advance of condenser C there are interposed series connected inductance L and condenser C at a position between condensers C and C an inductance L is connected between wire 14 and conductor 18. At a position beyond condenser C serially connected inductance L and condenser C, are interposed between wire 14 and conductor 18.

Typical values for the inductances and condensers of unit 15 are given below. For the moment it will sufiice to say that such components are so chosen that at frequencies below 80 cycles filter 15 prevents the flow of sufficient power to relay 27 to move its contactor 30 downwardly. Above 80 cycles per second the impedance of filter 15 drops sharply, such impedance then being low enough in the range 80 cycles per second (800 rpm. of shaft 13) to 290 cycles per second (2900 rpm.) to cause relay 27 then to cause contactor 30 to be moved into and be held in the lower inoperative position.

The second, 290 cycle high pass filter 20 is shown in detail in FIG. 5. Such filter includes the same number of components positioned in a manner identical with those in filter 15, the components differing, however, in value so that filter 20 presents a sufficiently high impedance to prevent operation of relay 40 in the range to 290 cycles per second (2900 rpm). At 290 cycles per second the impedance of filter 20 drops sharply and remains low through 360 cycles per second (3600 r.p.rn.), thereby permitting coil 40 of relay 39 to be energized. When the relay is thus energized, the circuit 42, 41, 45 is closed and the afterburner is operated.

The L pad attenuator 12 is shown in detail in FIG. 6.

A first resistor R is interposed between input wire 11 and output wire 19 leading to filter 20. Interposed between wire 11 beyond resistor R and filter 20 and ground is a second resistor R The lead wire 14 of filter 15 connects to wire 11 in advance of resistor R Attenuator 12 functions to match the alternator output impedance to the filter input impedance and also absorbs excess alternator power, especially at higher alternator speeds.

Typical illustrative but non-limiting values of the various circuit components above described are as follows:

C C .22 mfd.

L L 6.65 H 4,250 turns, #38 wire.

L 4.0 H 3,300 turns, #37 wire.

L L .45 H 950 turns, #31 wire.

L .27 H 735 turns, #30wire.

R 800 ohms.

R 200 ohms.

S 'S Hughes Aircraft, silicon diodes HD 6002.

Relay No. 1 Sigma V, 51 64000 CDW-SCR. Relay No. 2 Sigma V, 51 64000 CDW-SCR.

The switches operate as follows: In the low speed range, from 0-800 r.p.m, (alternator), both the 80 cycle and the 290' cycle filters offer high impedance to both rectifier and relay circuits, preventing the flow of power necessary to operate the relays 27 and 39. Thus under such conditions the ignition system is energized, and the afterburner is deenergized. At 800 rpm. the alternator 10 is operating at a frequency of 80 cycles, which is the cut-off frequency, or the frequency that allows current to pass through the 80 cycle filter 15. The impedance of the 80 cycle filter drops at this point, allowing current to pass through the rectifier 24 and into the relay 27,

causing the relay 27 to open. The ignition system is thus deenergized. The impedance of the 80 cycle filter 15 remains low through 3600 r.p.m. (360 cycles) allowing current to flow through the whole speed range, keeping the relay 27 open. The reverse is true as the speed is reduced to 800 r.p.m. The impedance of the 80 cycle filter then increases sharply and reduces the current to the relay 27 and allowing such relay to close, thereby again activating the ignition system.

The 290 cycle filter 20 operates in the same manner. Such filter acts as a high impedance to the second relay 39 at alternator speeds of from 0 to 2900 r.p.m. At 2900 rpm. theimpedance of filter 20 drops sharply, allowing current to pass through the filter 20 into the rectifier and closing the second relay 39. The afterburner is thus started. The impedance of filter remains low through 3600 r.p.m., keeping the relay 39 closed and the afterburner in operation. Upon reduction of the alternator speed to 2900 r.p.m., the 290 cycle filter impedance rises sharply, causing the relay 39 to open and afterburner openation to be stopped. From 2900 to 3600 r.p.m. both filters 15, 20 and relays 27, 39 are drawing power from the alternator 10.

Although only a limited number of embodiments of the invention have been illustrated in the accompanying drawings and described in the foregoing specification, it is to be expressly understood that various changes, such as in the relative dimensions of the parts, materials used, and the like, as well as the suggested manner of use of the apparatus of the invention, may be made therein without departing from the spirit and scope of the invention as will now be apparent to those skilled in the art.

What is claimed is:

1. In a variable speed engine of the jet type having a rotatable shaft driven in synchronism with the engine, said engine having a main burner, an afterburner, an ignition system for the main burner, and an ignition system for the afterburner, said ignition system for the main burner being operated in a low range of speed of the engine and the ignition system for the afterburner being operated in a high range of speed of the engine, and a speed responsive device for controlling said ignition systems, the improved speed responsive device which comprises an alternator driven by said shaft in synchronism therewith, two circuits connected in parallel to the output of the alternator, a high pass filter in each of said circuits, the filters in the respective circuits having different cut-off frequencies, and a relay in each circuit connected to the output of the respective filter for controlling further separate circuits of the respective ignition systems.

2. An apparatus as claimed in claim 1, wherein the relay controlling the circuit of the main burner ignition system is resiliently biased toward circuit-closed position, and the relay controlling the circuit of the afterburner ignition system is resiliently biased toward circuit-open position.

3. An apparatus as claimed in claim 2, comprising an attenuator interposed between the alternator and the filters to match the alternator to the filter input impedances and to absorb excess input power at higher speeds of the engine.

References Cited in the file of this patent UNITED STATES PATENTS 2,167,007 Schott et al July 25, 1939 2,178,290 Sorensen Oct. 31, 1939 2,231,174 Trogner Feb. 11, 1941 2,366,167 Adorjan Ian. 2, 1945 2,544,523 Bogdanoff Mar. 6, 1951 

